ALGAE ATTACK?

[manoj]

I think I have a problem(don't know whether it is). Many of my plants have a dark/black membrane like growth which covers the surface of the medium ?algae. it even covers the roots. When dry it peels off like paper. I tried removing it with an old mosquito forceps. I also tried repotting with new medium, but it always comes back PLEASE HELP

[King_of_orchid_growing:)]

It's algae.

It comes from your water supply.

They're harmless.

[manoj]

are you sure? because ever since these things appeared flowers/spike have gone down drastically. View file shot of Den. kasem white (taken 3yrs back). Now I get just 5 to 6 flowers/spike

[King_of_orchid_growing:)]

Actually, now that I think about it, let me be more specific...

I used the generic term "algae", 'cause I'm used to this misnomer from the tropical fish hobby. It's technically cyanobacteria.

Cyanobacteria - Wikipedia, the free encyclopedia

Cyanobacteria is what is generally known as "slime algae", when it really isn't a true algae.

I apologize for the confusion.



I really don't think that the reduced flower production necessarily means the cyanobacteria ("slime algae") was causing the problem.

Reduced flower production could be from a number of things.

Although I will say that if your media is growing cyanobacteria when you're growing Dendrobiums, there might be something wrong...

I think you may be growing them too wet.

Dendrobiums need to dry out completely between waterings.

If your Den hybrid involves a lineage that is heavy in Dendrobiums in the section Phalaenanthe, do know that they don't grow in areas that are very wet. Dendrobiums in the section Phalaenanthe tend to be lithophytic orchids and grow in areas that don't receive a massive amount of moisture. They originate from Australia. The precipitation they receive is actually seasonal (they technically can grow w/ a winter rest period, even though people don't do it).

Try growing them drier and giving them a winer rest. Provide plenty of light and see if that increases your plant's flower production and decreases the amount of cyanobacteria ("slime algae") you get.

[isurus79]

Algae in and of itself is not bad. But the pictures of the roots you posted looks like you might be watering too much. This would kill the roots and be the cause of your declining flower production. Can you post a better picture? Maybe one close up and one picture farther back so we can see what is going on with the roots. It looks a bit over watered to me.

[manoj]

sorry about the delay. As instructed by Isurus79 I am posting two more shots of the algae. The first one shows the medium covered with growth. Note how it bridges the gap b/w 2 pieces of brick at 2 and 3 '0' clock position. The second shot shows bits of membrane removed to expose the roots under. Sorry, I couldn't attach the first picture somehow.

[isurus79]

Well, I've never seen algae that thick before, so I would consider repotting or at least pull the roots out and see how they look. Then smell the root mass. If it smells sour, cut off all the dead roots and then repot it in new media. However, if the roots like fine, then replace the root mass and start diagnosing your flower decline from scratch. My guess is that the media sour though.